[Felicia:] You know, I'm sorry I didn't get to make my genetically modified blue tomatoes.
But on the other hand,
I have a new-found appreciation for mutant fruit and mutant friends.
[Caitlin:] Ah, thanks, buddy.
I realize I'm never going to live that one down.
Even though the tomatoes were a bit of a bust,
we did cover a lot of important material this week.
[Felicia:] That's right. We talked about the process of cloning and how scientists can
manipulate DNA in the laboratory using restriction enzymes and DNA ligase.
[Caitlin:] Our molecular scissors and molecular glue.
We also talked about what happens when things don't go quite right
and mistakes result in changes or mutations in the DNA.
[Felicia:] Remember, not all genetic change is bad.
There are many different types of mutations.
Some are harmful, some are neutral, and some can even be beneficial.
[Caitlin:] Yes, and sometimes just changing one base pair
can cause drastic changes in how proteins function.
[Felicia:] We also tried to clear up some of the confusion
surrounding genetically modified organisms, or GMOs.
GMOs are plants or animals that have had
their genetic material modified through genetic engineering.
[Caitlin:] You know, I'm always a little bit fuzzy about GMOs because it can be difficult to distinguish
between changes that are the result of traditional farming practices
and those that are engineered in the laboratory.
[Felicia:] Yup. I haven't given up on that blue tomato yet.
[Caitlin:] I know you haven't.
Hey, if you want even more practice manipulating DNA,
you can head over again to Labster, our virtual laboratory.
Put your skills to the test and try out our molecular cloning simulation. [Music]
[Caitlin:] Last week, we introduced you to sickle cell disease.
Individuals suffering from sickle cell disease have
a single amino acid mutation in their hemoglobin gene.
[Felicia:] There is a rich scientific history surrounding the discovery of
sickle cell anemia and unravelling this disease
has provided several firsts for human genetics.
Linus Pauling, remember him?
He's the guy who got the structure of DNA wrong.
Oh, and by the way, he won not one but two Nobel prizes. But I digress.
Linus Pauling was the first to describe sickle cell disease as
a genetic condition caused by differences in the hemoglobin protein.
[Caitlin:] When we reviewed the organization of our genome in Week 1
we said that the nucleus holds 23 pairs of chromosomes.
What we didn't say is that one chromosome from each pair is
inherited from your mother and one chromosome is inherited from your father.
This means that you have two copies of each gene.
In the case of sickle cell anemia,
if you have two normal copies of hemoglobin,
then your red blood cells are round and doughnut shaped. No problem.
If you have two faulty copies on the other hand,
you have sickle cell disease.
The abnormally-shaped red blood cells can cause blockages in
blood vessels preventing the surrounding tissues from receiving oxygen.
But, what happens when you have one normal copy and one faulty copy?
[Felicia:] I'm actually really glad you asked.
Back in the 1950s,
Dr. Anthony Allison noticed something curious.
The frequency or number of individual with one normal copy and
one faulty copy was high in certain regions of East Africa.
In places with high rates of malaria,
the number of people with one mutated copy of the gene was also much higher.
Dr Alison thought that this trait may confer a selective advantage against malaria.
Several years of studies later,
this hypothesis proved correct.
Individuals with a single mutated copy of
the beta globulin gene are more resistant to malaria.
[Caitlin:] Bet you didn't see that one coming!
If you have one faulty copy of hemoglobin,
it's actually an advantage if you live in areas that have higher rates of malaria.
This is just one example of how studying and understanding our genome helps
reveal connections between genetic and infectious disease that might otherwise be missed.
Next week, we'll find out how scientists are working to unlock ancient genomes of humans,
pathogens, and plants alike.
Caitlin MullarkeyAssistant Professor
Felicia VulcuAssistant Professor
